The present invention relates to a new and distinct variety of Prunus rootstock which will hereinafter be denominated varietally as the ‘A B 207 Rootstock’. This rootstock is particularly tolerant to the Armillaria fungus, commonly known as causing a destructive root and crown rot of the tree.
The Armillaria fungus is commonly referred to as the Oak Root Rot or Honey Fungus. The fungus is a potent parasite on many fruit tree crops including stone fruit. The usual species associated with this malady is A. mellea. This fungus has global distribution in stone fruit cultivation and is prevalent in the Central Valley of California, where oak trees are common. When such oak trees are removed or die, the fungus tends to remain in the ground. Subsequent plantings of virtually any tree or vine in the vicinity where the oak tree had been planted, usually result in some degree of infection of the planted tree crop. The disease is typified by non-random spread along tree rows due to root anastomosis between adjacent trees, providing an ideal infection route for this root infecting fungal pathogen. Most plants are eventually overcome by the fungus. Mature trees usually succumb over several years, generally leading to entire orchard death. The fungus can survive in the soil for long periods of time (years), and currently no prophylactic chemical control is available. Generally fumigation is utilized prior to new plantings to eradicate the fungus. However, due to the wide host range of this fungus, the fungus is rarely eliminated but usually only partially controlled.
Long term durable control of soil-borne diseases is most effectively achieved through plant tolerance selection. However, in the case of resisting Armillaria in stone fruit, numerous different rootstocks have been tried in diverse geography including California with little success. This new discovery represents a significant improvement in the development of a rootstock tolerant to this serious pathogen. In addition, the rootstock of the present invention is useful for varieties such as ‘Crimson Glo’ (U.S. Plant Pat. No. 12,856) and ‘Black Splendor’ (unpatented) and ‘Joanna Red’ (U.S. Plant Pat. No. 10,385) and the rootstock of the present invention appears to also be available for use with peach and nectarine (Prunus persica) scions.